Less lethal weapon projectile

ABSTRACT

A less lethal weapon projectile having an overall cylindrical shape and including a front end ( 4 ) shaped as an at least approximately spherical cap and a rear end ( 2 ) includes: a core ( 6 ) made from aluminium foam, having an overall cylindrical shape and including a front end ( 16 ) and a rear end ( 13 ) with a rear face ( 14 ), the front end ( 16 ) shaped as an at least substantially spherical cap; a base ( 5 ) assembled with the rear end ( 13 ) of the core ( 6 ) and including a front wall ( 9 ), arranged transversely and covering the rear face ( 14 ) of the core ( 6 ); and an outer case ( 7 ) covering at least the front end ( 16 ) of the core ( 6 ). The center of gravity and the center of thrust correspond perfectly, so that the projectile has good external ballistics.

This invention relates to less lethal weapon projectiles, able to impacta target such as would a violent stroke of the fist while limiting thedamage and or the traumas induced by this impact, in particular on thesensitive and unprotected zones of an individual (in particular thehead).

LLW projectiles (for Less Lethal Weapon) are conventionally used by lawenforcement and the armed forces in exterior operations, with thepurpose of neutralizing or to cause to flee certain individuals,avoiding injuring them or minimizing the injuries or lesions incurred.

These projectiles are shot using rifled launch tubes of which the mostcommon are of a caliber of 40 mm (NATO designation: 40 mm×46).

Very generally, these LLW projectiles have an overall cylindrical shapeof which the length is of a magnitude of 50 to 70 mm and of which thediameter, as specified previously, is of a magnitude of 40 mm, with afront end in the shape of an overall demi-spherical cap. They areconventionally carried out by molding thermoplastic foam.

Today, prior is rather poor in the field of research on new kineticmunitions that are less lethal (LL) and in particular in the improvementof the terminal effect of the corresponding projectiles.

Indeed, prior embodiments aimed to render more ductile the materialscomprising these projectiles thinking that the more the projectile is“soft” the less lethal it is. As far as the applicant is aware, noconcrete thought has been given as to the understanding of therelationships between the physical parameters and the lesion effectsduring the impact of an LL projectile on a human target. Theidentification of the “correct” physical parameter makes it possible tosearch for pertinent technical solutions.

In order to respond to this objective, a study was carried out anddemonstrated and validated through tests and simulations:

-   -   that energy is not the universal mechanical parameter of        severity    -   that this parameter is in fact the force at the impact.

Recall that controlling the low likelihood of causing a fatal outcomewith a less lethal projectile, serious injuries or permanent lesions onan individual is not easy to obtain due to a physical phenomenon that iswell-known to ballistics experts which is the loss of speed over thetrajectory of the projectile, caused by the resistance of the air to theprogression of the latter. As such, with current projectiles, a very lowlevel of effectiveness can be had at a distance of 50 m and asubstantial level of deleterious effects at 10 m, which poses enormousproblems of use for law enforcement and the armed forces.

As was said previously, the physical parameter that is important at theimpact from the point of view of lesion effects is the force at impactexerted on the target.

In order to improve the effectiveness and not the lethality of lesslethal projectiles, the main objective of the invention is to transmitto the impact a programmed force which is always the same, orsubstantially the same, regardless of the terminal speed, andcorrelatively regardless of the firing distance (and this within theconventional ranges of speed at the time of impact (i.e. about between50 to 100 m/s).

For this, the LLW projectile according to the invention, which has anoverall cylindrical shape of longitudinal axis L, comprising a front endin the shape of a spherical or approximately spherical cap and a rearend, is characterized by the fact that it comprises:

-   -   a core made from aluminum foam, said core has an overall        cylindrical shape centered on said axis L, comprising a front        end in the shape of a spherical or substantially spherical cap,        and a rear end with a rear face,    -   a base assembled with said rear end of the core, said base        comprises a wall, arranged transversally to said axis L, which        covers said rear face of said core, and    -   an outer case covering at least the front end of said core.

The base of the projectile is deformed during the firing by thescratches of the tube of the weapon which allows for the putting intorotation of the projectile.

The core made of aluminum foam is very light and it offers thecharacteristics of crushing and of absorbing energy that are veryinteresting, homogeneous and independent of the speed of deformation inall directions; the outer case makes it possible to optimize theballistic flight of the projectile and to lessen at the moment of impactthe first projectile-target contact.

The force of impact of this projectile is constant or almost constantregardless of its speed (in the conventional ranges of impact speed, inparticular between 50 and 100 m/s). This impact force is in particularaccording to the density of the aluminum foam, a parameter chosenaccording to the force of impact sought.

Preferably, the density of the aluminum foam used for the core of theLLW projectile in accordance with the invention is between 30 and 300kg/m³.

The base of the projectile is advantageously made from thermoplasticmaterial and its case of thermoplastic foam.

According to an interesting characteristic, the transversal wall of thebase is extended towards the rear by a tubular wall, centered on thelongitudinal axis L, delimiting an opening rear cavity.

According to a particular embodiment, the transversal wall of the baseis extended towards the front by a tubular extension, centered on thelongitudinal axis L, in order to form a housing for the reception of therear end of the core made of aluminum foam.

According again to a particular embodiment, said rear tubular wall, orsaid front tubular extension, comprises an annular exterior ring forguidance.

According again to a particular embodiment, the transversal wall of thebase is extended towards the front by an axial tenon allowing for thecentering of the front portion of the projectile.

According again to another particularity, the outer case extends to therear base to cover the entire exposed face of the core.

In a particularly interesting embodiment, the rear end of the outer casecomprises a bead, directed inwards, which penetrates into an annularreceiving groove arranged in the core made of aluminum foam.

In this case, the front end of the base advantageously covers the rearend of the outer case, in order to lock into position said bead in thereceiving groove.

In addition, the front end of the base and the rear end of the outercase cooperate more preferably through complementary shoulders.

On the other hand, the core can comprise an axial recess opening intoits rear face facing the front transversal wall of the base. This recessmakes it possible in particular to program two levels of impact force byselecting two densities of aluminum foam. It can remain as is or befilled by a more or less dense aluminum foam, in order to program theseverity of the impact.

According again to a particular embodiment, the projectile comprises anannular contraction between its front and rear ends, corresponding to adecrease in diameter, said contraction extends towards the frontstarting from the front end of the base.

This particularity has in particular for objective to prevent thecontact of the base as an inclined impact with the target.

On the other hand, the projectile in accordance with the invention cancomprise a structure made of a reversible deformation material, insertedin the front, on the axis L, between the outer case and the core. Thismaterial can be a thermoplastic foam or be comprised of microbeads.

The base, the core and the outer case of the projectile are carried outindependently and they are assembled together by any suitable means.

The invention will be further illustrated, without be restricted in anyway, by the following description of several possible embodiments, givensolely by way of example and shown in the annexed drawings wherein:

FIG. 1 is a perspective view of an LLW projectile in accordance with theinvention;

FIG. 2 is an axial cross-section view of the projectile of FIG. 1;

FIG. 3 is an axial cross-section view of a first alternative embodimentof the projectile in accordance with the invention;

FIG. 4 is a perspective view of a second alternative of the projectilein accordance with the invention;

FIG. 5 is an axial cross-section view of the projectile of FIG. 4;

FIGS. 6 and 7 are curves showing the variation of the force during theimpact according to time for projectiles according to the invention;

FIG. 8 is an axial cross-section view of a third alternative of theprojectile in accordance with the invention.

The LLW projectile 1 shown in the FIGS. 1 and 2 has an overallcylindrical shape of longitudinal axis L. Its length can be of amagnitude of 50 to 70 mm and its diameter of a magnitude of 35 to 45 mm.

The rear end 2 of this projectile 1 terminates according to a planeperpendicular to the longitudinal axis L. At this level, an openingaxial recess 3 allows for the conventional receiving of a certainpyrotechnic propulsion, or other method of propulsion. Its front end isin the shape of a spherical or approximately spherical cap.

This projectile 1, symmetrical around its longitudinal axis L, iscomprised of a rear base 5, extended towards the front by a core 6 ofwhich the external face is practically entirely covered by a case 7.

The rear base 5 comprises a cylindrical tubular wall 8, centered on theaxis L, which is closed on its front end by a transversal wall 9. Thetubular wall 8 is not closed towards the rear, and, with the fronttransversal wall 9, it delimited the aforementioned axial recess 3.

Facing this front transversal wall 9, note that the tubular wall 8comprises a single-piece annular ring 10 which extends as a projectionoutwards. The outside surface of this ring 10, of overall cylindricalshape, defines the maximum outside encumbrance of the projectile and itconstitutes a guiding face inside the barrel of the propulsion weapon.

The outside surface of the tubular wall 5 has a diameter that is a fewmillimeters less than that of the guiding surface of the single-piecering 10.

On the side of the face 11 directed towards the front end 4 of theprojectile, the transversal wall 9 of the base 5 comprises a cylindricalsingle-piece tenon 12, centered on the axis L. This tenon 12 has adiameter of a magnitude of half of the diameter of the projectile 1; itsheight is of a few millimeters.

The base 5, comprising the tubular wall 8, the transversal wall 9, thering 10 and the tenon 12, is carried out as a single piece by moldingthermoplastic material (polycarbonate for example). The density of thethermoplastic material used can be of a magnitude of 1200 to 1600 kg/m³.

It has for function to give the projectile a substantial portion of itsmass, allow for its propulsion and the connection at the front of theportion that absorbs the energy and programming the force of impact.

The core 6 of the projectile 1 has an overall cylindrical shape centeredon the axis L.

Its rear end 13 has a diameter that is slightly less than the diameterof the guiding surface of the ring 10 of the base 5, and its rear face14 is structured to hug the front face of this base 5, with the tenon12.

For this, this rear face 14 extends in the plane of the front face 11 ofthe base 5, and it comprises an axial reservation 15, corresponding tothe shape of the tenon 12.

The front end 16 of the core 6 is in the shape of a spherical orapproximately spherical cap, centered on the axis L.

This core 6 can have a length between 30 and 50 mm. It is made fromaluminum foam (honeycombed structure of aluminum) of which the densityis advantageously between and 300 kg/m³. The length of the core 6 andthe density of the aluminum foam used are according to the force ofimpact sought and according to the quantity of energy to be absorbed.

The core 6 is carried out by molding or any other method of forming ormachining of honeycombed materials.

For example, an aluminum foam is used manufactured by the company CYMATCorporation (Canada) under the designation “Cymat stabilized aluminumfoam” (registered trademark), or by the company SHINKO WIRE CO Ltd(Japan), under the designation “Alporas” (registered trademark).

Such a core structure 6 has for function to limit at the impact theimpact force predetermined beforehand during the absorption of theenergy, regardless of the impact speed of the projectile. The shape atthe front of this honeycombed structure in addition makes it possible toretain the time for coming to force of the impact, until nominal level,below the critical burst value of the scalp for example.

The rear end 13 of the core 6 is assembled with the front end 11, 12 ofthe base 5 by any suitable means, for example by gluing.

The front end 16 of the core 6 is covered by the case 7 madeadvantageously from thermoplastic foam; the density of thisthermoplastic foam is advantageously between 100 and 150 kg/m³. Forexample rubber, an EPDM material or a nitrile-teflon mixture (registeredtrademark) can be used.

This outer case 7 has a thickness of a few millimeters (for example 1 to3 mm, advantageously of a magnitude of 2 mm).

In the embodiment shown, it covers all of the front and lateral externalsurface of the core 6, except for a an annular strip 18 of the rear end13 of said core 6. So that its external surface is located in theextension of the external surface of this “free” annular strip 18, thecase 7 is housed in an adapted reservation 19 arranged on the externalface facing the core 6.

This case 7, is the shape of a tube closed at its front end by aspherical or substantially spherical cap, is fixed onto the core 6 byany suitable means, for example by gluing.

The case 7 has for function to improve the ballistic flight of theprojectile, prevent at the first target-projectile contact the localbursting of the biological material of the target and allow for thepre-crushing of the honeycombed structure of aluminum.

FIG. 3 shows an alternative embodiment of the projectile of the FIGS. 1and 2. The portions that are identical to the preceding embodimentretain the same marks in order to facilitate comprehension.

In the corresponding projectile 1′, the core 6 comprises a blind axialrecess 20 that opens into its rear face 14. This recess 20advantageously has a cylindrical shape of which the diametercorresponds, to the nearest clearance, to that of the axial tenon 12 ofthe base 5. Its function is to make it possible to carry out during theimpact an impact force profile at two levels programmed beforehand,according to the severity sought.

Still in the alternative embodiments, the recess 20 can be filled withan added material. This added material can for example consist of analuminum foam that is denser than that used for the periphery of thecore 6, in such a way as to increase the effectiveness of the impact ofthe projectile.

For this projectile 1′, note that the length of the core 6 is less thanthat of the projectile core 1 of FIGS. 1 and 2.

FIGS. 4 and 5 show another possible embodiment of a projectile inaccordance with the invention.

Here again, portions that are identical to the embodiments of FIGS. 1 to3 retain the same marks in order to facilitate comprehension.

The corresponding projectile 1″ comprises a rear base 5, extendedtowards the front by a core 6 made from aluminum foam of which theexternal face is covered by a case 7.

Note that the tubular wall 8 of the base 5 is extended towards thefront, beyond the transversal wall 9, by a tubular single-pieceextension 21. The guiding ring 10 extends facing the transversal wall 9of the base 5, over a portion of the tubular wall 8 and over practicallyall of the length of the extension 21.

This extension 21 and the wall 9 of the base 5 form a housing 22 forreceiving the rear end 13 of the core 6. The single-piece tenon 12 ofthe preceding embodiments is no longer present.

Here again, the core 6 and the base 5 are assembled by any suitablemeans, more preferably by gluing.

On the other hand, in this embodiment, note that the case 7 covers allof the exposed surface of the core 6; it extends to the base 5, and inparticular to the front end of the extension 21.

The embodiment of FIGS. 4 and 5 is also distinguished from the precedingones, by the presence of a contraction 23, corresponding to a reductionin diameter, between is rear 2 and front 4 ends.

This contraction 23 has for function to prevent, as an inclined impactof the projectile, the plastic base-target contact, preventing as such alevel of contact impact that is incompatible with the programming of theefforts by the aluminum foam.

It is substantially obtained by a decrease in the diameter of the rearend 13 of the core 6.

The presence of the contraction 23 confers upon the core 6 a particularlongitudinal section, with a rear end 13 of cylindrical shape extendedby a front end 16 in the shape of a bead or bulge, of an overallspherical shape.

The surface of the front end 4 of this projectile 1″ is particular: thespherical end surface 4 a is extended by a truncated cone surface 4 bwhich itself is extended by a cylindrical surface 4 c (of which thediameter corresponds approximately to the diameter of the ring 10) whichis again extended by a “re-entrant” surface 4 d ending at thecontraction 23. This particular shape of the front end 4 of theprojectile 1″ makes it possible to calibrate the rate of the increase ineffort (level of the force programmed over the time taken to reach it),thus preventing the local bursting of the biological structures (scalpfor example as a cranial impact).

The shapes of these projectiles all have a perfect correspondencebetween their center of gravity and their center of thrust in order toobtain good external ballistics.

FIG. 6 is a curve showing the variation of the force during the impactaccording to the impact time, for the projectiles 1 and 1″ of FIGS. 1and 2, on the one hand, and 4 and 5 on the other hand.

The following are distinguished:

-   -   the rate of climbing (constant force a over the rate of climbing        b).

This rate of climbing must be less than a critical value in order to notburst the biological surface structures,

-   -   the constant level of the force a programmed by the density of        the aluminum foam and the geometry of the core.

This level a is calibrated in order to determine beforehand the damageand the severity sought.

-   -   the end of the impact c, still with a constant or substantially        constant force a.

FIG. 7 shows the force/time variation for a projectile with doubledensity (such as shown in FIG. 3). The level d is obtained by theperipheral foam of the core, and the level e is defined by the centralfoam of the core of which the density is higher than the peripheralfoam.

FIG. 8 further shows another possible embodiment of a projectile inaccordance with the invention.

In the corresponding figure, the portions that are identical to theembodiments of FIGS. 1 to 5 retain the same marks in order to facilitatecomprehension.

This projectile 1′″ comprises a rear base 5 which covers the rearportion of a core 6 made from aluminum foam of which the external faceof the front portion is covered by a case 7.

The material used for these various portions 5, 6 and 7 correspond tothose described hereinabove in relation with the embodiments of FIGS. 1to 5.

As can be seen in FIG. 8, the case 7 covers the front portion of thecore 6, to the base 5.

On its rear end, this case 7 comprises a bead 24 protruding inwards,which penetrates into a reservation or annular groove 25 arranged in thecore 6 made from aluminum foam, providing for the assembly between thetwo elements 6 and 7.

This annular groove 25 of the core 6 extends in a plane perpendicular tothe longitudinal axis L of the projectile 1′″.

On the rear end of the case 7, note again the presence of a shoulder 26,directed outwards, facing the bead 24.

The setting in place of the case 7 on the front end of the core 6 iscarried out by forced embedding, thanks to the elasticity of thematerial that this case 7 is comprised of.

On its side, the base 5 comprises a rear transversal wall 9, which isextended towards the front by a tubular single-piece extension 21 whichcovers the rear end 13 of the core 6 made from aluminum foam.

The internal face of the transversal wall 9 is thrust against the rearface 14 of the core 6. The external face of the tubular extension 21comprises the protruding guiding ring 10.

On its front end, the extension 21 comprises an annular shoulder 27directed inwards. This annular shoulder 27 of the base 5 iscomplementary to the annular shoulder 26 of the case 7.

The base 5 is added on the rear end of the core 6, after the case 7 isset into place.

In this framework, its annular shoulder 27 covers the complementaryshoulder 26 of the case 7, in such a way as to lock the case 7/core 6assembly.

The base 5 is fixed onto the rear end of the core 6 by any suitablemeans, more preferably by gluing.

The internal face of the tubular extension 21 comprises more preferablystriations or a set of grooves/ribs which make it possible to optimizethe corresponding gluing.

On the other hand, more preferably, the base 5 and the case 7 are alsomade integral through gluing, on their complementary shoulders 26 and27.

After attaching, the external faces of the front end of the base 5 andof the rear end of the case 7 are located in the continuity of eachother.

The absence of gluing of the case 7 on the front end of the core 6 makesit possible to leave this case 7 free during the crushing and toprevent, or at least limit, the contact between the base 5 and thetarget, in offset impacts in relation to the longitudinal axis L.

If needed, the tubular wall 21 can be extended, towards the rear, beyondthe transversal wall 9, in order to comprise an opening rear cavity,similar to the cavity 3 present in the embodiments if FIGS. 1 to 5.

As shown in FIG. 8, the front end of the core 6 can be truncated inorder to allow for the positioning of a structure 28 (shown as a dottedline) making it possible to dampen the shock at impact.

This structure 28 can be added between the case 7 and the front end ofthe core 6; any shock-absorbing material with reversible deformation canbe used, for example a thermoplastic foam with a suitable duration, ormicrobeads (for example of a diameter between 0.5 and 2 mm, made from anelastomeric material or any other material with reversible deformation).

In an alternative embodiment, the shock-absorbing structure 28 can beobtained as a single-piece with the case 7, by the material comprisingthis case 7.

1. A projectile for less lethal weapon, having an overall cylindricalshape of longitudinal axis, said projectile comprising: a projectilefront end having a shape of a spherical or approximately spherical cap,a projectile rear end, a core made from aluminum foam, said core havingan overall cylindrical shape centered on said axis, comprising a corefront end in the shape of a spherical or substantially spherical cap,and a core rear end with a rear face, a base assembled with said rearend of the core, said base comprising a wall, arranged transversally tosaid axis, which covers said rear face of said core, and an outer casecovering at least the front end of said core.
 2. The projectileaccording to claim 1, wherein said core is made from aluminum foamhaving a density between 30 and 300 kg/m³.
 3. The projectile accordingto claim 1, wherein said base is made from a thermoplastic material. 4.The projectile according to claim 1, wherein said outer case is madefrom thermoplastic foam.
 5. The projectile according to claim 1, whereinthe transversal wall of the base is extended towards the rear by atubular wall, centered on said axis, delimiting an opening rear cavity.6. The projectile according to claim 1, wherein the transversal wall ofthe base is extended towards the front by a tubular extension, centeredon said axis, in order to form a housing for receiving the rear end ofthe core made from aluminum foam.
 7. The projectile according to claim5, wherein said rear tubular wall, or said front tubular extension,comprises an annular exterior guiding ring.
 8. The projectile accordingto claim 1, wherein the transversal wall of the base is extended towardsthe front by an axial tenon.
 9. The projectile according to claim 1,wherein said outer case is extended to the rear base to cover the entireexposed face of the core.
 10. The projectile according to claim 9,wherein a rear end of the case comprises a bead, directed inwards, whichpenetrates into an annular receiving groove arranged in the core. 11.The projectile according to claim 10, wherein the front end of the basecovers the rear end of the case in order to lock into position said beadin said groove.
 12. The projectile according to claim 11, wherein thefront end of the base and the rear end of the case cooperate throughcomplementary shoulders.
 13. The projectile according to claim 1,wherein the core comprises an axial recess opening into the rear face ofthe core facing the front transversal wall of the base.
 14. Theprojectile according to claim 1, which comprises an annular contractionbetween the front and rear ends of the projectile, corresponding to adecrease in diameter, said contraction extending towards the frontstarting from the front end of the base.
 15. The projectile according toclaim 1, which comprises a structure made of reversible deformationmaterial, inserted on the axis, between the case and the core.
 16. Theprojectile according to claim 2, wherein said base is made from athermoplastic material.
 17. The projectile according to claim 2, whereinsaid outer case is made from thermoplastic foam.
 18. The projectileaccording to claim 2, wherein the transversal wall of the base isextended towards the rear by a tubular wall, centered on said axis,delimiting an opening rear cavity.
 19. The projectile according to claim2, wherein the transversal wall of the base is extended towards thefront by a tubular extension, centered on said axis, in order to form ahousing for receiving the rear end of the core made from aluminum foam.20. The projectile according to claim 6, wherein said rear tubular wall,or said front tubular extension, comprises an annular exterior guidingring.